Even though i am a complete math junkie, and am in the last term of first year calculus--which i understand pretty well, i am often vexed by algebra. Seems ridiculous, don't it?

Anyway, along the way of solving the derivative of a parametric, to find the equations of tangent lines at a point, I've run into the road block that i show in the attachment.

Sorry that it's an attachment. Not so sue about latex yet (just joined up today) and i detest the thought of keyboard entered math stuff.

Thanks!